Spending on search engine marketing rose by 20 percent year-over-year during Q1 2010, according to data from search agency Efficient Frontier's quarterly U.S. Search Engine Performance Report. The research also found query and click volumes have risen while cost-per-click levels remain relatively stable – resulting in greater return on investment for advertisers.

The agency suggests reinvigorated spending from retail advertisers, as well as healthier investment from companies in the automotive and financial sectors, helped drive growth, with retailers reportedly spending an average of 32 percent more during Q1 2010 than they did during the same three months in 2009. Meanwhile, auto and finance advertisers spent an average of 9 percent more, year-over-year.